This invention is generally directed to photoresponsive imaging members, and more specifically the present invention is directed to layered photoresponsive members having incorporated therein pigment mixture compositions. Thus, in one embodiment the present invention envisions the selection of specific mixtures of photogenerating pigments in photoresponsive imaging members containing therein aryl amine hole transport molecules. The aforementioned photoresponsive imaging members can be negatively charged when the photogenerating layer is situated between the hole transport layer and the substrate; or positively charged when the hole transport layer is situated between the photogenerating layer and the supporting substrate. Additionally, the photoresponsive imaging members with the photogenerating pigment mixture compositions as photogenerator substances, and wherein the member further includes therein an aryl amine hole transport layer are useful in electrophotographic imaging processes, especially xerographic processes wherein negatively charged or positively charged images are rendered visible with developer compositions of the appropriate charge. These imaging members are sensitive to wavelengths of from about 400 to about 900 nanometers, thereby enabling their utilization with gas and diode lasers, light emitting diodes (LED), broad-band light sources such as tungsten, fluorescent, and xenon lamps. The broad spectrum response of the imaging members of this invention enable their selection for multifunction electrophotography processes employing the aforementioned light sources.
Layered photoresponsive imaging members are generally known, reference for example U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference, wherein there is described an imaging member comprised of a photogenerating layer, and an aryl amine hole transport layer. Examples of substances useful in the photogenerating layer of this patent include trigonal selenium, metal phthalocyanines, and metal free phthalocyanines. Additionally, there is described in U.S. Pat. No. 3,121,006 a composite xerographic photoconductive member comprised of finely divided particles of a photoconductive inorganic compound dispersed in an electrically insulating organic resin binder. The binder materials disclosed in the '006 patent comprise a material which is incapable of transporting for any significant distance injected charge carriers generated by the photoconductive particles.
Organic photogenerating pigments such as perylenes, bisazos, perinones, and polycyclic quinones are well known for electrophotography applications. Generally, layered imaging members with the aforementioned pigments evidence acceptable photosensitivity in the visible region of the spectrum and hence they are particularly suitable for electrophotogaphy process where visible light sources such as tungsten, fluorescent, and xenon lamps operate. However, these classes of pigments in many instances have low or negligible photosensitivity in the near infrared region of the spectrum, that is for example above 700 nanometers, thereby preventing their selection for photoresponsive imaging members in electronic printers wherein electronic light emitting devices, such as GaAs diode lasers, are commonly used as a light source to create electrostatic image on the imaging members. Also, some of the above mentioned organic pigments have narrow and restricted spectral response range such that they cannot reproduce certain colors present in the original documents; and inferior copy quality also results in these situations.
Moreover, the selection of phthalocyanine pigments as photoresponsive members in laser based electrophotography printers have been described in numerous patents. Both metal-free phthalocyanines and metal phthalocyanines have optical absorption in the region of 750 to 850 nonometers where GaAs diode lasers operate. Therefore, these spectral characteristics render phthalocyanines particularly suitable for use in conjunction with the lasers imaging process. Unfortunately, the phthalocyanines exhibit a low optical absorption in the wavelength region of from 450 to 550 nanometers. Therefore, when the phthalocyanine is selected for white light imaging processes, the lack of photosensitivity in this region results in some loss of red color copyability. Accordingly, the phthalocyanines are generally not suitable for use in the aforesaid photocopying applications, especially when the original documents possess red color images.
While the above-described photoresponsive imaging members are suitable for their intended purposes, there continues to be a need for improved members, particularly layered members, having incorporated therein specific pigment mixture compositions and aryl amine hole transport compounds. Additionally, there continues to be a need for layered imaging members comprised of specific aryl amine charge transport compositions; and as photogenerating materials pigment mixtures with panchromatic sensitivity, low dark decay characteristics, high charge acceptance values, and wherein these members can be used for a number of imaging cycles in a xerographic imaging or printing apparatus. Furthermore, there continues to be a need for photoresponsive imaging members which can be positively or negatively charged thus permitting the development of images, including color images, with positively or negatively charged toner compositions. Moreover, there continues to be an important need for disposable imaging members with nontoxic organic pigments. Also, there is a need for imaging members useful in xerographic imaging processes, and xerographic printing systems wherein, for example, light emitting diodes (LED), helium cadmium, or halium neon lasers, GaAs diode lasers are selected; and wherein these members are particularly sensitive to the visible and infrared region of the spectrum, that is, from about 400 to about 900 nanometers. Additionally, photoresponsive imaging members containing the pigment mixtures illustrated herein as a photogenerator layer are capable of performing mutlifunction electrophotography applications, such as white light photocopying and electronic printing.